INFERRED Hα FLUX AS A STAR FORMATION RATE INDICATOR AT z ∼ 4–5: IMPLICATIONS FOR DUST PROPERTIES, BURSTINESS, AND THE z = 4–8 STAR FORMATION RATE FUNCTIONS

Abstract

Inferred H flux as a star formation rate indicator at z 4-5: α ∼ implications for dust properties, burstiness, and the z = 4-8 star formation rate functions Copyright and reuse:Sussex Research Online is a digital repository of the research output of the University.Copyright and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable, the material made available in SRO has been checked for eligibility before being made available.Copies of full text items generally can be reproduced, displayed or performed and given to third parties in any format or medium for personal research or study, educational, or not-for-profit purposes without prior permission or charge, provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. ABSTRACTWe derive Hα fluxes for a large spectroscopic and photometric-redshift-selected sample of sources over GOODSNorth and South in the redshift range z=3.8-5.0 with deep Hubble Space Telescope (HST), Spitzer/IRAC, and ground-based observations. The Hα flux is inferred based on the offset between the IRAC 3.6 μm flux and that predicted from the best-fit spectral energy distribution (SED). We demonstrate that the Hα flux correlates well with dust-corrected UV star formation rate (SFR) and therefore can serve as an independent SFR indicator. However, we also find a systematic offset in the a b + SFR SFR HU V ratios for z∼4-5 galaxies relative to local relations (assuming the same dust corrections for nebular regions and stellar light). We show that we can resolve the modest tension in the inferred SFRs by assuming bluer intrinsic UV slopes (increasing the dust correction), a rising star formation history, or assuming a low-metallicity stellar population with a hard ionizing spectrum (increasing the a L SFR H ratio). Using Hα as an SFR indicator, we find a normalization of the star formation main sequence in good agreement with recent SED-based determinations and also derive the SFR functions atz 48 -. In addition, we assess for the first time the burstiness of star formation inz 4 galaxies on <100 Myr timescales by comparing UV and Hα-based sSFRs; their one-to-one relationship argues against significantly bursty star formation histories.

Unveiling the nature of brightz ≃ 7galaxies with theHubble Space Telescope

“…4). The presence of strong rest-frame optical nebular emission lines in the SEDs of 3 < z < 7 LBGs has now been demonstrated by several studies (Stark et al 2013;de Barros et al 2014;Smit et al 2014Smit et al , 2015Marmol-Queralto et al 2016). These previous results however, have focused on relatively faint LBGs selected from within the CANDELS fields or cluster-lensing fields imaged by HST.…”

ZFIRE: using Hα equivalent widths to investigate the in situ initial mass function at z ∼ 2

“…Multiple studies have investigated possibilities for IMF variation in galaxies using Balmer line flux in the context of probing SFHs (Meurer et al 2009;Weisz et al 2012;Zeimann et al 2014;Guo et al 2016;Smit et al 2016). Modelling effects of IMF variation using Hα or Hβ to UV flux ratios have strong dependence on the assumed SFH and dust extinction of the galaxies and is only sensitive to the upper end of the high mass IMF.…”

A gravitationally-boosted MUSE survey for emission-line galaxies at z ≳ 5 behind the massive cluster RCS 0224

“…Systemic deviations of ∼0.1 dex from the canonical value of ξ ion have been derived from the inferred Hα emission in typical z ∼ 4-5 UV-selected galaxies Rasappu et al 2016;Smit et al 2016). The bluest z ∼ 4-5 galaxies (β<-2.3), likely very young and dust-free sources, have a significantly higher Lyman-continuum photon production efficiency of log 10 ξ ion = 25.53-25.78 Hz erg −1 (Stark et al 2015;, in good agreement with our derived value for the z = 4.88 arc, which also has a blue UV-continuum colour (β = −2.2).…”